This disclosure relates to siloxane block copolymer nanoporous foams, methods of manufacture thereof and to articles comprising the same.
Foams having pores in the nanometer regime (e.g., aerogels having average pore sizes of less than or equal to about 100 nanometers) generally display superior thermal conductivity over foams that have pores having sizes that are greater than or equal to about 100 nanometers. The superior thermal conductivity of aerogels is attributed to the fact that air or vapor molecules in the pores cannot interact one another because the pore sizes prevent the molecules from traveling distances generally associated with their mean free paths.
While aerogels generally display superior thermal properties over other foams that have larger pore sizes, their mechanical properties such as, for example, their tensile strength, impact strength, and the like, are generally so low that they cannot even be manufactured in monolithic form. As a result of their inferior mechanical properties, they have to be compounded with other binders in order to manufacture a usable monolithic product. The compounding with other binders generally reduces the thermal conductivity of the usable monolithic product.
In addition to having inferior mechanical properties, aerogels are manufactured using supercritical extraction. The use of supercritical extraction involves the use of high pressures and high-pressure vessels, which are expensive and can be hazardous to personnel involved with the production and manufacturing of aerogels.
It is therefore desirable to manufacture foams having pores in the nanometer regime that display superior mechanical properties over aerogels. It is also desirable to manufacture foams by methods that are less expensive and hazardous when compared with processes involved with the manufacture of aerogels. Further, it is also preferable to have closed pore structure for improved mechanical properties. Aerogels usually have open porous morphology.